Power transmissions for automotive vehicles have undergone significant changes and progress over the years. Both manual selection of gear ratios and automatic selection of gear ratios have been undertaken. The use of both mechanical or synchronizer clutches and friction torque-transmitting devices have been employed.
Generally, the automatic transmissions have utilized hydraulically actuated friction devices and the manual transmissions have utilized mechanical synchronizer clutches. However, many current transmissions have automatic shifting capabilities and employ synchronizer type arrangements. These transmissions can therefore be made as manual or manually selected ratio transmissions or automatically selected ratio transmissions. Such devices might be of either a single input clutch or dual input clutch type of arrangement.